The present invention relates generally to formed copper bus bars, and more specifically, but not exclusively, to specialized bus bars and features thereof used to blend power electronics and arrays of semiconductors and other devices typically interconnected on circuit boards into a single hybrid structure.
An electric vehicle (EV) incorporates a hybrid set of technologies throughout its various systems. For example, there is an energy storage system that stores and distributes large amounts of electrical energy. The storage and distribution is controlled using high-performance semiconductor devices for very fast switching to drive an electric motor, among other purposes. There are many well-known challenges to combining these technologies in a single operational circuit.
These challenges include mechanical design and layout of the components, to allow very large currents to be routed and controlled. Bus bars in general are well-known for electrical power distribution. Simply, a bus bar is a thick strip of copper or aluminum that is designed to carry these very large currents and to distribute current to multiple devices within the equipment. It is known to provide flat strips as bus bars due to favorable heat distribution. For example, formed copper bus bars have been used in industry for decades to connect large semiconductor modules to their associated capacitors, DC bus, and output bus. An advantage of a formed bus bar is that it may be adapted to fit into a particular irregular-shaped volume, such as exist inside a propulsion system of an EV.
Similarly it is well-known to use circuit boards to connect and support large arrays of electronic components, including multilayer FR4 type circuit boards. Technologies have been developed to quickly and efficiently assemble and test a wide range of devices and connectors using circuit boards. Conventional solutions do not blend bus bars and circuit boards; they simply provide a bus bar for the high current and one or more separate conventional circuit boards, such as power electronics (e.g., gate drive electronics). Generally these circuit boards are planar and can be difficult to conform to irregularly-shaped volumes.
There are many potential inefficiencies in an EV regarding distribution and conversion of electrical energy. Some of these potential inefficiencies are exacerbated by segregating these functions. For example, current flow creates one or more magnetic fields and these in turn have an associated inductance. Inductance causes a voltage to be generated that is proportional to a rate of change of current in a circuit. For many reasons, inductance is one limitation on fast switching times and reducing inductance generally reduces inefficiencies in an EV circuit, particularly the important propulsion and power storage/distribution circuits. For a conductor having a thickness, a length, and a width, in general inductance is directly related to the thickness and length and inversely related to the width. For a current loop formed by two conduction paths, the inductance is directly related to the length of the paths and to the separation distance between the paths.
What is needed is a specialized formable low inductance high current capacity bus bar blending power electronics and arrays of semiconductors and other devices into a single hybrid structure.